Not in aircraft but in Rv's, Auto's Truck's, Etc... The purpose of using the body and frame as a ground is more for saving wire, at least this was the original concept, after computers started being added to control the engines, it was found that having parallel paths of current was causing many I/O errors and computer problems, and now we see that they have isolated most bonding to the frame and body to prevent this. it is still bonded but in one place only, to the engine block. but this bond is the second reason, it is to allow the opening of fuses. these are the only two reasons that the frame/body was bonded to.
Lightning uses the air as a conductor, if the body of a vehicle is in this path through the air, then lightning will see this path as a lower resistance, lightning cares less if the electrical inside of the vehicle is bonded to the body or not, lighting only wants to complete its path to earth.
To help with this higher content of carbon was added to tires to help dissipate static, and lightning, static at a gas pump could be bad for your health
I'm a little rusty on aircraft, but I do know they did at one time bond the systems to the air frame, but I think this was discontinued as having a fuse fail just because a wire made contact with the air frame was too dangerous, and if I remember right they now an isolated system with grounding monitors, so the system will still function, but can be fixed on the next landing.
as for lightning it's the same as a vehicle body, the body of an aircraft, is just a lower resistance path in the air that lightning can pass through hopefully without damage, they do bond many parts of the air frame together, but this is only to ensure, good conductivity of the lightning current, like an equal-potential bonding system we use around pools.
Electrical current does not need or require a bond to earth to function.